Optical methods for acquiring 3-dimensional (3D) geometric information may be largely classified into the passive vision and the active vision, and in general, the active vision achieves more accurate and rapid 3D geometric information acquisition than the passive vision. The active vision generally adopts a special light, and illuminates an identifiable light pattern onto a target surface using a laser or LCD/DLP projector, captures images of the target scene, and extracts 3D geometric information from the captured images. Prior art document presented below introduces technical means for acquiring depth information necessary for 3D broadcasting.
The light pattern illuminated according to the active vision may be a single point or a single line, and may be a very complex patter. When the illuminated light pattern is a single point or a single line, information carried on the light pattern is scanty, so a disadvantage is a small amount of 3D information that can be acquired from one image or any fixed number of images, and in contrast, when patterns in the shape of many points, lines or stripes are illuminated all at once, there is a disadvantage that it is difficult to distinguish each subpattern. Various methods using colors have been proposed to illuminate a large number of subpatterns all at once and effectively distinguish subpatterns, but they still have many problems including color inconsistency between original light patterns and its captured images, the influence of target surface color, and increased costs of hardware and software. Particularly, generation of color patterns itself requires high complexity and high costs, so it is desirable to use a monochrome pattern for development of low-cost depth sensors.
When a monochrome pattern is used, colors are fixed and only the luminous intensity can be adjusted, and thus it is very difficult to increase the number of identifiable subpatterns. Particularly, in order to prevent accuracy reduction caused by a low signal to noise ratio (SNR) like in the case of a continuous pattern such as a low-frequency sinusoidal pattern, and to improve the distinguishability between adjacent positions by high-SNR pattern imaging, it is desirable to use a binary pattern, in which the number of luminous intensity levels is limited to two. However, with a binary pattern, there is no method for effectively increasing the number of identifiable subpatterns in a single pattern image.